Inductor in series with Full Bridge SMPS transformer is good practice?

[Flyback]

Hello
We are doing a 300W full bridge converter. Vin=300-400VDC, Vout = 15V, F(sw)=120khz.
We would like to add a 10uH inductor in series with the transformer primary in order to reduce the overvoltage ring on the secondary diodes at FET switch on. Can you state why this does not appear to be a standard procedure, after all, it is an easy way of getting improvement with little or no downside.
(ltspice sim and schem attached)

 

[tcmtech]

Here's a web book for you that would be well worth reading and learning in detail.

**broken link removed**

 

[ronsimpson]

We would like to add a 10uH inductor in series with the transformer primary

I think this can also be done by changing the coupling of the transformer. Adding more LL.

 

[Flyback]

Thanks, actually, I am now wondering about it, looking at the voltage spike in the connection of the external leakage inductor and the transformer is a little worrying, I think this would also be the same if it were 'internal' leakage.

 

[ronsimpson]

I have used saturate-able coils in that spot.
Say your current is 10A and the coil saturates at +/-0.1A. At high current the little coil is not in circuit. As current passes through zero the coil nu-saturates and adds inductance. I have used this to fight ringing.